Composite panel

ABSTRACT

A continuous process for making a core for a composite panel comprising cutting spaced apart tongues in columns from a metallic sheet, the tongues being foldable about base lines in the columns each base line being separated from the next tongue in the column by a web; folding the sheet to form a castellated structure having continuous side walls constituted by the spaces between adjacent columns of tongues with the webs of adjoining rows respectively lying in spaced apart parallel planes and oppositely folding the tongues of adjoining columns to lie alongside adjacent side walls with their extremities remote from their base lines extending in an appropriate one of the planes. The invention also includes a composite panel comprising the core covered on each side with sheet material as well as a process for making such a panel.

FIELD OF THE INVENTION

This invention relates to a method of making the metallic core of acomposite panel; to a method of making the panel and to a panel usingthe core.

DESCRIPTION OF THE PRIOR ART

In the past it has been usual in the manufacture of composite panelshaving metallic non-solid cores for both the cores and the resultantpanels to be manufactured in batches. Although many kinds of non-solidcores have been used there has been a tendency to favour honeycombstructures as presenting good strength characteristics but these requirebatch production methods to be used. Both batch production and the useof cores of honeycomb formation are expensive and there is a significantmarket for cheaper panels having lesser strength characteristics.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved method of making a metallic core for a composite panel whichcan be produced from coiled sheet material in a continuous process, animproved method of making the panel incorporating the core and animproved panel.

According to one aspect of the present invention there is provided acontinuous process for making a core for a composite panel comprisingcutting spaced apart tongues in columns from a metallic sheetcharacterised in that the tongues are foldable about base lines in thecolumns each base line being separated from the next tongue in thecolumn by a web; folding the sheet to form a castellated structurehaving continuous side walls constituted by the spaces between adjacentcolumns of tongues with the webs of adjoining rows respectively lying inspaced apart parallel planes and oppositely folding the tongues ofadjoining columns to lie alongside adjacent side walls with theirextremities remote from their base lines extending in an appropriate oneof the planes.

Another aspect of the invention provides a process for making acomposite panel in which a core formed according to the precedingparagraph is passed continuously through profile compression means whichcloses the side walls closely against the tongues and in which aftersaid means, sheet material from second and third coils is passedrespectively on each side of the core and stuck thereto.

The invention also provides a composite panel comprising a core havingspaced apart tongues arranged in columns in a metallic sheetcharacterised in that the tongues are folded about base lines in thecolumns each base line being separated from the next tongue in thecolumn by a web; the sheet being castellated having continuous sidewalls constituted by the spaces between adjacent columns of tongues withthe webs of adjoining rows respectively lying in spaced apart parallelplanes and the tongues of adjoining columns lying alongside adjacentside walls with their extremities remote from their base lines extendingin an appropriate one of the planes and the core being covered on eachside with sheet material stuck thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the invention will now be described byway of example with reference to the accompanying drawing in which:

FIG. 1 is a diagrammatic view of a machine for continuous production ofa core and a composite panel,

FIG. 2 is a third angle projection of part of a sheet to form a core,

FIG. 3 is a similar view of a core folded from the sheet of FIG. 2 withthe tongues cross-hatched for clarity, and

FIG. 4 is a fragmentary view of part of a sheet with a modified tongueshape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1 this shows a machine for making a core andcomposite panel according to the present invention. The machine isarranged for in line intermittent and continuous operation and comprisesa first coil 1 of aluminium alloy mounted on a decoiler 2, sheet 3 fromthe coil 1 is fed through rollers 4 and successively through an oiler 5and a shearing station 6 of known type. The sheet 3 then passes throughfurther guide rolls 7 to a known castellation former 8 and a knownbending station 9. Because of the nature of shearing, castellationforming and bending it will be understood that the operation of themachine so far described is intermittent.

Turning now to FIG. 2 this shows the sheet 3 after passing through theshearing station 6 and having been slit to form tongues 10 each foldableabout a notional base line 11. The tongues are in spaced apart columnssuch as 12 and 13 extending transversely to the direction of movement"A" of the sheet 3. The base line 11 about which each tongue can befolded is separated from the end extremity 14 of its adjacent tongue bya web 15 and it will be appreciated that with the arrangement of FIG. 2the webs 15 of adjoining columns are in alignment. Each column such as12 and 13 is separated by a space 16.

Having passed through the shearing station 6 for slitting the sheet 3 isthen repeatedly folded in the castellation former 8 to form thecastellated profile of FIG. 3 the folds being along the slit sides ofthe tongues 10. The tongues 10 of each column such as 12, 13 are nowfolded up and down such that they close the ends of the castellatedprofile. The tolerance of the slitting and folding operations are suchthat the side edges of the tongues 10 contact the continuous side walls17 of the core which are themselves formed by the spaces 16 of the sheet3.

It will be seen from FIG. 3 that the webs 15 of adjoining columns oftongues 10 such as 12 and 13 in FIG. 1 now respectively lie in spacedapart parallel planes represented by the width of the side walls 17which now constitute the width of the core structure and the extremities14 of the tongues extend in the plane of one set of the webs 15.

Reverting now to FIG. 1 when the castellated core, now indicated at 18,leaves the bending station 9 it passes downwardly over a guide roll 19to be looped at 20 through a degreasing bath 21. From the bath the corepasses over a guide roll 22 and through a set of profile compressionrolls 23, 24 into a heating chamber 25. It will here be understood thatthe loop 20 can vary in size to accommodate the intermittent movement ofthe core 18 leaving the bending station 9 and continuous movementthrough the rolls 23, 24. It will also be understood that the profile ofthe core 18 readily allows it to bend around an axis at right angles toits direction of travel.

The rolls 24 are arranged to rotate more slowly than the rolls 23 sothat "bunching" of the castellated core 18 takes place. This isdesirable for subsequent formation of a composite panel since both thenatural spring in the sheet material and the bending through thedegreaser 21 cause the edges of the tongues 10 to move away from thewalls 17. From the rolls 24 the bunched core passes into the chamber 25.

Second and third coils 26 and 27 of sheet material 28 and 29 aredisposed on decoilers 30 and 31. The sheet material may be of plasticsbut will usually be metallic and of aluminium alloy. The sheet 28 passesover a guide roll 32 and then over a succession of rolls 33, 34, 35, 36and 37 creating a "box" 38 so that the final strand 39 of the sheet 28extends horizontally with its inner surface uppermost. From the roll 37the sheet 28 passes into the heating chamber 25 and is applied to theupper surface of the core 18 at rolls 40, 41. The sheet 29 passes overguide rolls 42, 43 and 44 and then into the heating chamber 25 and isapplied to the lower surface of the core 18 at the rolls 40, 41.

Adhesive applicators 45 and 46 are respectively located within the box38 and on the inner side of the sheet 29 after the roll 44. Theseapplicators drip feed adhesive on to the inner surfaces of both sheets.The preferred adhesive is a water foaming polyurethane which is held inthe applicators under an inert atmosphere such as nitrogen. Water jets47 and 48 apply a fine spray to the adhesive coating just prior to thejoining of the sheets 28 and 29 with the core 18 at the rolls 40, 41 soas to promote foaming of the adhesive. Foaming enables the adhesive tospread between the walls 17 of the core 18 so as to engage the sideedges of the tongues 10 as well as around the outer edges 14 of thetongues and over the edges of the webs 15. The composite panel 49 thusformed in the heating chamber 25 passes through pinch rolls indicatedgenerally at 50 to consolidate close contact between the core 18 and thesheets 28 and 29. Beyond the chamber 25 the panel 49 is cut intosections 51 by a flying saw 52.

By using a polyurethane adhesive the temperature within the chamber 25may be maintained at 50° C. to 80° C. which enables the sheets 28 and 29to be pre-painted on their outer surface without the paint finish beingdamaged within the chamber 25.

Although the composite panel 49 is preferably formed as described aboveit will be understood that the continuously formed core 18 could be cutinto sections and panels made by batch production techniques. In suchcase the necessary bunching of the core can be performed in a suitablejig (not shown). Such batch production method is essential for theformation of curved panels using precurved covering sheets. It wouldalso be possible to stick only one of the sheets 28 or 29 to the core 18in the machine of FIG. 1; subsequently bend the partly formed panel in ajig and then apply the other panel.

It is envisaged that panel sections 51 produced in aluminium alloy inthe machine of FIG. 1 could have a width up to 1600 mm a maximum lengthof 12 meters. The coils 1, 26 and 27 could be up to 10 tonnes. It isexpected that the panels would have a flatness within a tolerance of 0.4mm per meter length.

The results indicate that the performance of the panel is only slightlyinferior to that of the honeycomb product when used with the same epoxyadhesive. The choice of the polyurethane adhesive is dictated by cost,by the ease of using the system within an automated line and it has beenfound to provide a panel of adequate strength.

Once the panel sections 51 have been cut it will be understood that inseparate operations various edge closing methods may be employed. Theseinclude bending and crimping or sticking excess material of the sheets28 and 29; incorporating a separate metallic edging member and pluggingthe edges with a plastics filler.

When the panels are of aluminium alloy it is expected that they willhave a total thickness of 10 mm to 25 mm.

Although as described above the tongues 10 are rectangular it will beunderstood that their side edges could be inclined towards one anotherso that the walls 17 are also inclined. FIG. 4 of the drawingsillustrates the limit of this possibility with the tongues 10 beingtriangular, as at 52. In this case opposed walls 17 would adjoin at theapex of the triangles to provide hollow triangular beams extendingtransverse to the arrows `A`. The excess material 53 could be punchedout and wasted or bent to be stuck to the walls 17.

The resultant panel is not as strong as panels having a conventionalhoneycombed core but nevertheless has a multitude of uses where highstrength is not so important, in view of the economy that can beprovided by continuous production.

The strength of the core shown in FIG. 3 could also be increased forexample by staggering the tongues 10 in each column in the sheet 3 sothat the webs 15 are not in alignment with one another on opposite sidesof the core. Another modification could be to increase the spacing ofthe tongues in the columns so that they are long enough for theirextremities 14 to be folded over to lie in the planes of the appropriatewebs 15.

I claim:
 1. A continuous process for making a core for a composite panelcomprising cutting spaced apart tongues in columns from a metallic sheetcharacterised in that the tongues are foldable about base lines in thecolumns each base line being separated from the next tongue in thecolumn by a web; folding the sheet to form a castellated structurehaving continuous side walls constituted by the spaces between adjacentcolumns of tongues with the webs of adjoining rows respectively lying inspaced apart parallel planes and oppositely folding the tongues ofadjoining columns to lie alongside adjacent side walls with theirextremities remote from their base lines extending in an appropriate oneof the planes.
 2. A process according to claim 1 in which facing sheetsare secured to the formed core in the same continuous process to form acomposite panel.
 3. A process according to claim 1 in which metal sheetfrom a first coil is passed intermittently successively through aslitting mechanism for forming the tongues in the plane of the sheet; acastellation former and a tag bender.
 4. A process for making acomposite panel in which a core formed according to claim 1 is passedcontinuously through profile compression means which closes the sidewalls tightly against the tongues and in which after said means, sheetmaterial from second and third coils is passed respectively on each sideof the core and stuck thereto.
 5. A process according to claim 4 inwhich the core and said sheet material is passed through a heatedchamber containing pinch rolls for the panel which, in conjunction withthe profile compression means, maintains the core with its side wallsclosed tightly against the tongues.
 6. A process according to claim 5 inwhich each sheet material has its outer surface pre-painted and theinner surface is coated with an adhesive before passing through thechamber and the temperature of the latter is sufficiently high to causethe adhesive to set but sufficiently low that the pre-painted surfacesare not damaged.
 7. A process according to claim 6 in which thetemperature is between 50° C. and 80° C.
 8. A process according to claim7 in which the adhesive has a polyurethane base.
 9. A composite panelcomprising a core having spaced apart tongues arranged in columns in ametallic sheet characterised in that the tongues are folded about baselines in the columns each base line being separated from the next tonguein the column by a web; the sheet being castellated having continuousside walls constituted by the spaces between adjacent columns of tongueswith the webs of adjoining rows respectively lying in spaced apartparallel planes and the tongues of adjoining columns lying alongsideadjacent side walls with their extremities remote from their base linesextending in an appropriate one of the planes and the core being coveredon each side with sheet material stuck thereto.
 10. A composite panelaccording to claim 9 in which sheets are metallic and their outersurfaces are pre-painted.
 11. A composite panel according to claim 9 inwhich the core and the outer sheets are of aluminium alloy.